What Is a Market Depth Chart? How to Read Liquidity

A market depth chart is a visual representation of the buy and sell limit orders waiting in an order book at different price levels. It displays cumulative order volume on both sides of the market, helping traders assess available liquidity and identify where larger orders could affect execution prices.

Candlestick charts show how prices have moved, but they do not reveal the full range of orders currently waiting to be filled. During volatile trading, limited liquidity can lead to wider spreads, partial fills (where only part of your order is executed) and unexpected slippage (getting a worse price than you expected).

Understanding how to read a depth chart can help traders assess these execution risks before placing an order. This guide explains how depth charts work, what liquidity walls reveal and why visible order-book data has important limitations.

What Is a Market Depth Chart?

A market depth chart is a graphical view of the resting buy and sell orders displayed in an electronic order book. Market depth chart meaning, in plain terms: a picture of where buy and sell orders are resting at each price.

It typically uses Level 2 market data (a live feed of the resting orders beyond the best bid and ask) to show available order volume across multiple price levels.

The underlying concept is market depth, which refers to the liquidity available to absorb buy and sell orders without causing substantial price movements. A depth chart makes this information easier to interpret by displaying cumulative order volume as two opposing curves.

Unlike a candlestick chart, which tracks historical price movements, a depth chart focuses on orders that have not yet been executed. It helps traders see where visible buying and selling interest is concentrated and how much displayed liquidity is available at different prices.

The same information can also appear in a Depth of Market (DOM) ladder. A DOM presents price levels and their corresponding order sizes in a numerical table, while a depth chart converts these figures into cumulative volume curves.

Both provide insight into the order book, but they present the information differently.

One important distinction is that a depth chart only reflects the orders included in its data feed. Depending on the exchange, broker or platform, the chart you’re using may not show liquidity available through other venues or hidden order types.

How a Market Depth Chart Works

The chart uses two axes to display order-book liquidity.

The horizontal X-axis shows the asset's price, usually increasing from left to right. The vertical Y-axis measures cumulative resting order volume, which represents the total displayed quantity available across successive price levels.

The chart normally has three main components:

• Green Bid Curve (Left): This shows cumulative buy limit orders at or below the best bid. Moving left towards lower prices adds more resting buy orders to the total, causing the curve to rise in steps.
• Red Ask Curve (Right): This represents cumulative sell limit orders at or above the best ask. Moving right towards higher prices adds more resting sell orders, increasing the cumulative volume.
• Central Gap (Bid-Ask Spread): The gap between the highest available bid and the lowest available ask represents the spread. A narrow spread generally indicates closer buying and selling quotes, while a wider spread can increase the cost of immediate execution.

The height of either curve does not necessarily represent one large order. Because the chart displays cumulative volume, each price level adds its resting orders to the total from the preceding levels.

For example, suppose an order book shows 50 shares offered at $100.01 and another 150 shares at $100.02. The cumulative displayed sell volume reaches 200 shares by $100.02.

If a market buy order for 200 shares arrives and those orders remain available, it could execute across both price levels rather than at a single price. The actual fill depends on the liquidity available when the order reaches the market.

This is why the shape of a depth chart matters. It shows how displayed liquidity is distributed, helping traders understand how a larger order might affect the average execution price.

However, the order book changes continuously, so what you see is only a snapshot. New orders can appear, existing orders can be cancelled, and transactions can reduce available volume within milliseconds.

Reading Buy Walls, Sell Walls, and Liquidity Slopes

The shape of the chart can reveal where resting orders are concentrated and where visible liquidity is relatively limited.

A sharp vertical step, commonly called a liquidity wall, indicates a substantial amount of displayed order volume at or near a particular price level.

A buy wall forms when a large quantity of buy limit orders is concentrated at a lower price. Traders may interpret this as an area of potential support because incoming sell orders could be absorbed by resting buyers.

A sell wall represents a concentration of sell limit orders above the current price. It may act as temporary resistance if buying pressure is insufficient to absorb the available sell volume.

Neither wall guarantees that price will stop or reverse. Resting orders can be executed, reduced or cancelled, allowing the market to move beyond the level.

By contrast, a relatively flat section of the cumulative curve indicates that little additional displayed volume is available across those price levels. If an aggressive order exceeds the available liquidity, it may execute across several prices.

This directly affects which order type you choose: market vs limit orders.

A market order prioritises execution at the best available prices. When liquidity is limited, it may receive fills across multiple price levels, resulting in a less favourable average execution price than expected.

A limit order sets the maximum price a buyer is willing to pay or the minimum price a seller will accept. If it cannot execute immediately, it may rest in the order book and add visible liquidity. However, execution is not guaranteed, and marketable limit orders (limit orders priced to match an existing order straight away) may fill immediately rather than remain in the book.

In practice, it is useful to observe how liquidity changes as the price approaches a visible wall, rather than relying on the wall's size alone.

For example, during a fast-moving market session, buyers may push prices towards a large concentration of sell orders. If those orders absorb the incoming buying pressure, the market could stall or pull back. If the orders are filled or cancelled, prices may continue rising through the level.

This is why a single depth chart snapshot can be misleading. Comparing changes in displayed liquidity with actual executed trading volume gives you more context than assuming a large order wall will hold.

The Blind Spots: Spoofing, Hidden Orders, and CFD Reality

Although these charts provide useful information about resting orders, they do not show every source of available liquidity or guarantee how prices will behave.

Some orders may disappear before execution, while other trading activity may take place outside the visible order book.

One important risk is spoofing, a form of market manipulation in which a participant places orders with the intention of cancelling them before execution.

These orders can create a misleading impression of strong buying or selling interest. When they are cancelled, the apparent liquidity disappears, potentially leaving other traders exposed to unexpected price movements.

However, not every cancelled order is evidence of spoofing. Traders and market makers routinely update or withdraw legitimate orders as market conditions change. Intent is an important distinction.

Visible depth charts also have several other limitations:

• Iceberg Orders: Some trading venues allow large orders to display only part of their total quantity. As the visible portion is executed, additional volume may become available from the hidden reserve. A depth chart therefore may not reveal the full size of an order.
• Dark Pools: Certain institutional orders are matched through off-exchange trading venues without their details being displayed in the public order book beforehand. These orders are not necessarily reflected in a standard depth chart.
• CFD Execution Structures: When trading Contracts for Difference (CFDs), the displayed liquidity may come from a broker's pricing system or aggregated liquidity providers rather than a central exchange. Order execution depends on the broker's pricing arrangements, available liquidity and execution model.

These limitations matter when interpreting the relationship between displayed depth and actual trading costs.

A market with relatively little resting volume does not always produce poor execution. Liquidity providers may replenish their quotes quickly enough to absorb incoming orders. Equally, a market displaying substantial depth can become difficult to trade if orders are withdrawn during a sudden price movement.

For leveraged CFD traders, the consequences can be particularly serious. Wider spreads, slippage and rapid market movements can increase trading losses, while leverage magnifies the effect of price changes on account equity.

The Financial Conduct Authority (FCA) reported in December 2022 that approximately 80% of CFD customers lose money. This is a general figure cited by the regulator, not a fixed loss rate for every provider. UK CFD firms must disclose their own proportion of loss-making retail client accounts in their risk warnings.

During periods of market stress, liquidity can change rapidly, spreads may widen and execution prices can differ from those initially displayed. A depth chart can help you recognise these risks, but it can’t eliminate them.

Conclusion

A market depth chart helps traders understand how displayed buy and sell orders are distributed across different price levels. Market depth chart explained in one line: it maps displayed liquidity, but it does not forecast price.

By examining liquidity walls, cumulative volume and the bid-ask spread, traders can better assess where larger orders might affect execution.

However, visible liquidity is not a reliable prediction of future price movements. Resting orders can disappear, hidden orders may not be displayed, and the quality of execution depends on more than the depth chart alone.

Understanding order types in trading can help traders choose execution methods that suit their objectives and the prevailing market conditions.

Market depth is best used as a tool for assessing liquidity and execution risk, alongside your own price analysis and position sizing. This is especially important when trading leveraged products, where slippage and rapid price changes can lead to substantial losses.